With recent environmental legislation, vehicle fuel economy has become a great concern. An effective way of reducing fuel consumption is to decrease the mass of vehicular components.
The fuel tank is a component which must meet a certain vehicle durability requirement. To reduce fuel tank mass, its thickness can be diminished but not to the expense of its ability to meet the durability requirement. Therefore, there is a need to find a way of decreasing the mass of the fuel tank assembly while maintaining the rigidity of its structure.
Currently, the stresses in a fuel tank are managed through the choice of material, wall thickness and geometric shape and section properties of the tank shell. The geometry and section properties are constrained by the forming limitations of the material, the available package space in the vehicle environment and the desired fuel tank volume capacity. The wall thickness is generally established for the worst case local stress condition within the geometry of the shell. The shell thickness required for the localized worst case stress is applied approximately uniformly over the entire surface of the tank shell. Much of the tank carries a heavier wall thickness than required to meet the localized stress therefore increasing the total mass of the tank above the optimum level.
In order to overcome these and other drawbacks, the prior art teaches the use of supports, reinforcements, or the like, which provide additional structural rigidity to the tank assembly. However, there is no teaching of positioning such supports in localized areas of the tank shell, which are subjected to heavier levels of pressure and deflection. Instead, the prior art typically teaches providing reinforcements that span along the entire surface of the tank shell's walls. Still, when localized reinforcement is taught, such elements do not however enable a reduction in the thickness of the entire tank shell, and accordingly a reduction in the total mass of the tank.
What is therefore needed, and an object of the present invention, is an improved fuel tank assembly comprising support members, which provide support to areas of the tank shell that exhibit high levels of stress while also achieving a reduction in the thickness of the fuel tank shell.